As far as I recall it stared in 2014 or so, yes metrics could/were still gamed, but there was still a belief in VC that OSS projects could turn into Red Hats. First I heard of it was when a VC told me they were "looking for the next docker" and mentioned something about Rancher OS and how quickly it's stars/follows were growing. In VC you tend to have conviction builders, and conviction buyers. I suppose what happened was some conviction builders used growth of a project on gh as part of a leading indicator (valid or otherwise), and conviction buyers picked up on that as a method.